Electromagnetic control with magnetic shunt safety means



Aug. 26, 1958 J. H. THORNBERY ET AL 2,849,653

ELECTROMAGNETIC CONTROL WITH MAGNETIC SHUNT SAFETY MEANS Filed Jan. 21,1953 3 Sheets-Sheet l .Zfassell B. Ha ZZcws 2 haw. 10114441 bm mmv @n mmI Nb 1958 J. H. THORNBERY ET AL 2,849,653

ELECTROMAGNETIC CONTROL WITH MAGNETIC SHUNT SAFETY MEANS Filed Jan. 21,1953 s Sheets-Sheet 2 INVENTORS: z-fofwz H T/iOP/L'fiill] fussed! Z9.Naif/bears Aug. 26, 1958 J. H. THORNBERY ET AL 2,849,663

ELECTROMAGNETIC CONTROL WITH MAGNETIC SHUNT SAFETY MEANS Filed Jan.21,1953 3 Sheets-Sheet 3 INVENTORS: T/B/an J7. Thor/21961,?

fiassell B miffiems- B r Hy p.140, ladluu United States PatentELECTROMAGNETIC CONTROL WITH MAGNETIC SHUN T SAFETY MEANS John H.'Thornbery, Whitefish Bay, and Russell R. Matthews, Wauwatosa, Wis,assignors to Base Inc, a corporation of Wisconsin Application January21, 1953, Serial No. 332,464 1 Claims; (Cl, 317-197) This inventionrelates to control devices, and has to do with electromagnetic operatorsfor valves controlling flow of fuel to burners and provided with meansfor automatically shutting off flow of fuel in the event ofextinguishment of the burners.

In the copending application of Floyd J. Bydalek and Russell B.Matthews, Serial No. 270,666, filed February 8, 1952, there is disclosedan electromagnetic control device in which a control valve is operatedby electromagnetic means effective for opening and'closing the valveresponsive to requirements or variations in conditions to be controlled,for example, variations in temperature in a space to be heated. Thecontrol valve is actuated by a rotor turnable in an air gap ofelectromagnetic means the effective strength of the magnetic field ofwhich is varied responsive to variations in the conditions to becontrolled and, in conjunction with means yieldingly urging the valvetoward one position in opposition to the magnetic field, is effectivefor opening and closing the control valve.

The present invention is in the nature of an improvement in theelectromagnetic control means of the above identified copending.application. It is directed to the provision of safety means effectivefor interrupting how of fuel to a main burner inthe event ofextinguishment of an associated pilot burner'and' whether or nottheconditions to be controlled:are then callingfor-suppl-yof fuel to themain burner, such means also assuring that flow of fuel to the mainburner will remain cutoff during resetting of the safety'means; To thatend, we provide means whereby the electromagnetic operator means isrendered ineffective when the pilot burner is extinguished. The safetymeans comprises a magnetic shunt for the electromagnetic operator means,held in an ineffective position so long as the pilot burner is lit andmoved to effective position responsive to extinguishment of the pilotburner. More'particularly, we provide a bridging member of high magneticpermeability held out of cooperative relation to the core of theelectromagnetic operator means when the pilot burner is lit, and movedinto cooperative bridging relation to the core of the electromagneticoperator means responsive to extinguishment of the pilot burner,eifectivefor shunting around the air gap of the latter means asubstantial portion of the magnetic flux thereof and therebyrenderingthe electromagnetic operator means ineffective for openingthecontrol valve. Themeans for holding the bridging member ininoperative or ineffective position comprise electromagnetic meansenergized by thermoelectric generator means heated by the pilot burner,

extinguishment of the'latter causing deenergization' of theelectromagnetic means and movment of =the bridging member to itsoperative or effective position; A further the above identifiedcopending application and may read.

ily be incorporated therein without necessity for any substantial changein such device. Further objects and advantages of our invention willappear from the detail description.

In the drawings:

Figure 1 is an axial sectional view'of an electromagnetic control deviceembodying the safety means of our invention;

Figure 2 is a plan view, on an enlarged scale, of the electromagneticoperator means of the device of Figure 1, with the cover and the partscarried thereby removed, certain parts being omitted for clearness ofillustration and certain other parts being broken away;

Figure 3 is a sectional view, on an enlarged scale, taken substantiallyon line 33 of Figure l, partly broken away;

Figure 4 is a fragmentary sectional view, on an enlarged scale, takensubstantially on line 4-4 of Figure 1;

Figure 5 is a fragmentary plan view, on an enlarged scale, of the coreand the rotor of the electromagnetic operator means and associatedparts;

Figure 6 is a side view of one of the combined biasing spring andcontrol valve supporting members; and

Figure 7 is a perspective view of the rotor of the device shown inFigure 1.

It will be helpful to describe first the electromagnetic operator andcontrol means with which the safety shutoff means of our invention iscombined; Such means comprises a valve body 1 having a fluid inlet 2 anda fluid outlet 3, A valve member 4 cooperates with a valve seat 5 at theoutlet 3 to control the flow of fluid through the valve, for example,the flow of gaseous fuel to a burner hereinafter referred to. It will benoted that the controlled fluid tends to hold the valve member 4 closed.This may, of course, vary within the scope of the invention.

The valve body 1 has an opening 6 covered by an enclosure 7 forelectromagnetic operating means hereinafter described, the bottom wall7a of enclosure 7 affording a plate-like cover for opening 6 and beingsecured in place, for example, by screws (no-t shown), threaded ableform. The particular core selected for illustration is of generallyrectangular configuration, comprising a pair of parallel side legs 10and 11 magnetically connected by parallel end legs 12 and 13.

The core is arrangedin position with its legs surrounding arms 7b ofbase plate 7a which arms serve to locate the core laterally whileabu-tmen-ts 7] (Figure 2) integrally formed in the base plate 7a serveto locate the core lengthwise thereon. The sidelegs 10 and 11 of thecore 9 have spaced pole pieces 14 and 15 formed, for example, asintegral parts of the core laminations, which pole pieces are ofconfiguration best shown in Figure 2 and have arcuate inner edgesdefining with arms 7b of the base plate 7a a'well in which the rotor 8is adapted to turn.

As best illustrated in Figure 1, the core is completed by a split corecomprising a first cylindrical core piece 16 located at the bottom ofthe aforementioned well and The enclosure 7 is prefi attached to baseplate 7a, and a second cylindrical core piece 17 suspended in said wellfrom above, core piece 17 being supported therein by a plate 18 restingon suitable abutments formed at the upper ends of arms 7b and held inposition by suitable means to be described later. The plate thispreferably non-magnetic and suitably insulated with lacquer, anodizingor other means, to reduce eddy currents.

The rotor 8 is of magnetic material, such as steel preferably fabricatedby powder metallurgy techniques, and is of form best illustrated inFigure 7. In general, the rotor t:- is of H-shape in vertical section asshown in Figure l and comprises a pair of arcuately for-med arms 8a and8b joined by a connecting portion 80 midway between the ends of thearms. The connecting portion 8c is adapted to be positioned between thesplit core pieces 16 and 17 which provide bearing surfaces therefor asillustrated by the bearing 20 mounted on the shaft 21 which extendsthrough and is non-rotatably connected to the rotor 8,

and by the thrust bearing comprising a ball 22 and a bowed leaf spring23 having a base 23a secured by screws 19 to arm '75 of base plate 7 andoverlying plate 18 effective for holding it in position.

As shown in Fi ures 1 and 2, the core pieces 16 and 17 are radiallyspaced from the upstanding arms 71': and pole faces 14 and 15 asufficient distance to afford clearance for the arms 8a and 8b of rotor8 through 360 of rotation. The split core diminishes the amount ofmaterial necessary in the rotor 3 and hence decreases its inertia, whileat the same time defining a relatively small air gap between the polepieces of core 9 and the core pieces 16 and 17. As will be apparent,this air gap need be no greater than the clearance needed for the armsof rotor 8 at each of the pole faces 14 and 15.

The power unit further comprises a primary winding 26 adapted to beconnected to a suitable source of electrical energy, and a secondarycoil or winding 27, the circuit of which may include conditionresponsive means such as the thermostat illustrated schematically at 28in Figure 1. It will be understood that when the primary winding 26 isenergized, and the secondary circuit is open, the magnetic flux createdin the core 9 will tend to flow around the core through the end leg 12upon which the secondary winding is mounted, in preference to jumpingthe air gap between pole faces 14 and 15, whereas when the secondarycircuit is closed, induced currents in the secondary winding 27 willdivert the magnetic flux across the aforementioned air gap to causemovement of the rotor as will hereinafter be described.

As shown in Figure l, the shaft 21 connected to rotor 8 extendsdownwardly through a sleeve 29 carried by core piece 16 and extendingthrough base plate 7a, the lower end of shaft 21 being connectednon-rotatably, but adjustably to one end of a crank member 30. Aresilient or rubber-like O-shaped ring 31 is mounted in an annulargroove near the lower end of shaft 21 and within sleeve 29 to provide agastight seal therebetween.

As best shown in Figure 3, the crank member 36 is non-rotatablyconnected to the shaft 21 as by a pin 32 for transmission of anymovement of rotor 8 to crank member 3t). At the opposite end of thecrank is a downwardly extending pin 33 off center with respect to theaxis of rotation of shaft 21. The pin 33 is adapted to engage a yoke 34(Fig. 1) connected at one end as by a stem 35 and pin 36 to valve member4.

The aforementioned yoke-valve member assembly is preferably suspended inthe valve body 1 as by a pair of springs 37 attached as by screws 38 toa portion 70 of the base plate 7 extending downwardly through opening 6of the valve body. The springs 37 serve both to support the valve memberassembly in alignment with the valve seat 5 and to bias both the rotor 8and valve member 4 as will hereinafter become apparent. When the baseplate 7 carrying and enclosing the power unit aforementioned 4 isremoved and/or replaced, the valve member assembly is removabletherewith as a unit.

The springs 37, as best shown in Figure 6, are of flat spiralconfiguration in side elevation and conically helical in edge elevationwhen uncompressed but numerous other configurations are contemplated.That is to say, when the turns are in a plane as shown in Figure 1 theyare under compression and imparting a sealing force to valve member 4against its valve seat 5. Movement of the valve member 4 to openposition against the bias of springs 37 further compresses the latter.In this regard while, as aforementioned, the ends of the outermost turnsof the springs 37 are attached to base plate portions as aforedescribed,the innermost turn in each case is attached to the yoke assembly as at39 and 40.

The enclosure 7 is further provided with openings 7d and 7e forelectrical conduit connections for the windings of the power unit, whilethe open top thereof is preferably provided with a cover 41 ofnon-magnetic material and of suitable form.

The valve member 4 selected for illustration is, in general, of the typemore fully disclosed in the copending application of Carl Wolff, SerialNo. 194,505, filed November 7, 1950, but may, of course, be of othersuitable form.

The mode of operation of the aforedescribed device is as follows:Assuming the primary coil 26 to be energized, as it will be underordinary circumstances, since the device inherently has a very lowstand-by power loss, a magnetic flux will be created in the core 9 in aclockwise direction as viewed in Figure 2, the flux as aforementionedflowing through the leg 12 of core 9 so long as the circuit of secondarywinding 27 remains open. The rotor 8 is angularly disposed on shaft 21so that in unenergized condition the leading edges of the rotor orarmature arms 8a and 3b are barely within the air gaps between the polefaces 14 and 15 and the core pieces 16 and 17; that is, a very smallportion of the rotor 8 is presented to the pole faces 14 and 15respectively as shown in full line in Figure 2. It is, of course,understood that the angular disposition of shaft 21 and hence rotor 8when unenergized is determined by the bias afforded by the springs 37,also supporting and biasing the valve member 4. In the embodimentillustrated in Figure 1, the seating of valve member 4 against the valveseat 5 under the bias of springs 37 limits the rotation of rotor 8 andprovides a stop therefor in its unenergized state.

When the circuit of secondary winding 27 is closed, as for example, byclosure of the contacts of the thermostat 28, the magnetic flux of core9 will no longer flow through leg 12 thereof, but will be diverted tothe pole pieces 14 and 15. Since the flux will cross the air gap thereinat the point of minimum air gap, and since the minimum air gap occurs atthe points where the leading edges of the rotor 8 are presented to thepole pieces, the magnetic fiux will be concentrated at those pointsimparting a counterclockwise torque to the rotor 8. The inherenttendency of the device is to tend toward a condition of minimum air gap.Hence the rotor 8 will be rotated into the air gap until the arms 3a and8b thereof are in registry with the pole faces 14 and 15 respectively asshown in dotted lines in Figure 2. Further rotation of the rotor 8 willnot occur since such movement would tend to increase the air gap, andmovement of the leading edges of the arms 8a and 8b beyond the polefaces would set up magnetic forces creating a torque in the oppositedirection. The rotor 8 is thereby afforded a magnetic stop limiting itsrotation in counterclockwise direction as viewed in Fig ure 2 to aposition wherein the arms of rotor 8 are in registry with the pole facesof core 9 as aforedescribed.

The foregoing phenomenon may be further elucidated by reference to themathematical relationships involved which may be expressed as follows:

where F istheforce of attraction brought to bear upon the rotor 8expressed in pounds, B isthemagnetic flux density, and A is the areaofrotor 8 presented to the pole piecesM- and 15. From this relationshipitwill also be seen that the device described inherently imparts agreater force at the beginning of the stroke than at the end thereof,since A (the area of the rotor. presented to the pole pieces) increasesas the rotor approaches registry with the pole pieces and F variesinversely with A. For example, if the rotor area presented to the polepieces is .0508 square inch when the rotor is unenergized and the totalarea of the rotor arms which may be presented to the pole pieces when inregistry therewith is .71 square inch, the force at the beginning of thestrokewill be 13.95 times the force exerted at theend of the stroke.This relationship has obvious advantages in that the rotor torque variesinthe same manner as the forces required to operate a mechanismrequiring greaterforce to initiate movement thereof than to maintainsuch novement, as for example, a valve member such as member 4 whichmust be moved against fluid pressure initially.

It is, of course, understood that rotation'of the rotor 8 and consequentmovement of valve member 4through the linkage of shaft 21, crank member30 and yeke 34 is against the bias of springs 37, which return. both thevalve members 4 and rotor 8 to their initial positions upondeenergization of the rotor as, for example, by re opening of thethermostat 2.8. In this connection, it may beobserved that the springrate of.the'biasing means may be matched to the torque characteristicsof the rotor to enhance its desired characteristic.

It should be further noted that such return will be prompt and withoutdanger of stieking since the rotor 8 never seals against the pole.pieces 14 and 15; that is, the air gap therebetween, although minimizedby registration of the rotor arms with the pole pieces, is nevercompletely eliminated and remains constant throughout the life of thedevice. The device istherefore not subject to residual magnetism of; thecore 9, thedifferential inthe flux valve required to pick up,the rotorand that at which itwill. drop out is greatly minimized, therebyrendering the control extremely sensitive andfast acting. Anotherdesirable feature ofthe afo-redescribed device is that it is inherentlymore efficient than known electromagnetic operators as, for example, thepower requirement is about one third that of a conventional solenoidoperator capable of actu ating a valve of the same size.

Asuitably formed cover 41 of aluminuin or any suitable non-magneticmetal or alloy, conveniently formed as a die casting, is removablysecured, in any suitable manner, on the enclosure orhousing 7. AU-shaped yoke or bridging member 45 isslidably mountedon vertical guiderods 46 fixed to and extending. downward from top. wall 47 of. cover 11(Figure ;4). The yoke 45 is formed of iron or any suitablemetal or alloyof high magnetic permeability and is of a width to bridge the core 9 ofthe electromagnetic operator means, with the lower ends of its arms. 43seating on legs. and 11 ofcore 9,

-when yoke 45 is lowered into its operative or effective position.

A T bracket is fixed to the upper face of the bight portion 51 of yoke45, centrally thereof, and has a transverse pin 52 secured therethroughadjacent its upper end. The pin 52 extends through slotted fingers of aforked head 53 at the inner end of the upper arm 54 of abell crank lever55 pivoted at 56 in a mounting bracket 57 having a base 58. secured,conveniently by riveting, to avertical wall 59of cover 41. The verticalwall 59 joins one end. of top wall 47 of cover .41 to a lower auxiliarytop wall 60 thereof andbase 58 of bracket 57 extends downward beyondwall 60, as shown in Figure l. A horizontally disposed operating rod 61is provided at its outer end with a reducedextension 62 of squared crosssection which is slidable through a corresponding opening in; thelowerend portionoi base, 5813f bracket V 6 57.. A pin 65. is securedthroughrod 61, a. short dis-' tance in advance of extension 62 thereofgitndvextends through slotted. fingers, of a forked head64 at the lower endofthe lower arm 65 of the bell crank lever 55. Under normal operatingconditions the rod 61 is held in its retracted position shown in Figure1, by means to be described presently, and is then effective for.holding 'the yoke 45 in its raised ineffective position providing airgaps of substantial extent between the lower ends of arms 48 of yoke 45and the legs 10 and 11 of core 9. When in its raised ineffectiveposition the yoke 45 has no appreciable effect upon the flow of.magnetic flux through core 9 and does not interfere in any way with theoperation of the electromagnetic operator means as and for the purposesabove described.

A fuel gas. supply pipe or conduit 67 is connected to the inlet 2 ofvalve body 1, and a pipe or conduit 68 connects the outlet 3 to a mainburner 69 of suitable known type. The burner 69 may be located in the.firebox of a furnace or, spaceheater, or any suitable apparatus, theenclosure about burner 69 preferably being vented to atmosphere. A-pilot burner- 70 of suitable known type is mounted adjacent main burner.69. for igniting gas flowing therefrom, as is known, and is connected tothe interior of valve body 1 by a gas supply tube 71. A thermo-electricgenerator, preferably inthe form of a thermocouple 72 of suitable knowntype, is mounted on pilot burner 70 in proximity thereto and disposed tobe heated thereby. The. thermocouple 72 may be of the general characterof that disclosed; and claimed in the Oscar J Leins Patent No.2,126,564, although any suitable, thermocouple may be.used. .It has twothermocouple members joined together to form a fhot junction, which isheated by a flame of the pilot burner 70, an outer tubular leadconductor .73 connected at one end to one of the thermocouple membersand an inner lead conductor 74 connected at one end to. the otherthermocouple member and mounted within and electrically insulated fromconductor '73. The other ends of lead conductors 73 and. 74 aredetachably connected in insulated relationto a terminal connector orfitting 76 in an end wall 77 of cover 41. The lead ,conductors73 and 74are connected, through fitting 76 and coiled flexible leads 78 and 79 tocoils 80 wound,up,on the arms of a Ueshaped core 81 ofan electromagnet82.

The electromagnet 82 is,disposed .within a cylindrical housing 83 in theouter end of which is secured av base 84 to which the core.81 is fixed.A cupped spring seat member v85, of greater diameter than. housing 83.and concentric therewith, is secured to base 84. 'Seat member 85 has anupwardly extending finger. 86 provided with a squared opening andslidable on a squared supporting and guide pin,87 secured through adownwardly extending arm 88 of an angle bracket 89fixed to top wall 47of .cover 41. The bracket 89 is provided at its outer end with a pair ofdepending ears 91 betweenwhich a bell crank lever 92 is pivoted on a pin93. ".The lower arm 94 of lever 92 is curved atits lower portion andextends downward between two spacedears 95 extending outwardly fromspring seat member 85 and between the latter and a pin 96 secured inears 95. The upper arm 97 normally is held raised and in contact with astop 98, secured through top wall 47 of cover 41, by a compression coilspring 99 seating at its upper end'on arm 97, about a rounded boss 100secured thereto, and seating-at its lower end in a depressed portion 101of cover 41, about a rounded boss 102 therein. A plunger 103, slidablein a housing 104 secured to top wall 47 of cover 41, normally is held inretracted position by a compression spring 105 within housing 104confined between the bottom wall thereof and a shoulder 106 at theupper-end of plunger 103. A reset button 107 is secured to theupper endof plunger 103,-.the lower. end of which is; in. close proximity to,orin contact with, the upperfacesof arm 7 97 of lever 92, when thelatter is in its normal position shown in Figure 1.

When bell crank lever 97 is in its normal position shown in Figure 1, itholds the housing 83, with the electromagnet 32 therein, in its outerposition toward the right, as will be clear from what has been said. Theoperating rod 61 is slidable through a reduced neck 109 of housing 83and has secured thereon, inwardly beyond neck 109, a cup shaped springseat member 110 similar to member 85.- A light compression spring 111 isdisposed about the electromagnet housing 83 and seats at its ends in themembers 85 and 110. Under normal operating conditions, the pilot burner70 is burning, the coils 80 of the electromagnet 82 are energized,effective for holding an armature 112, secured on the end of rod 61Within housing 83, seated on the pole ends of electromagnet 82, and thehousing 83 is held in its outer position. The bridging member or yoke isthen held in its ineffective raised position and the electromagneticoperator then functions in its intended manner, as above explained.

In the event the pilot light is extinguished, the thermocouple coolsthus deenergizing the coils 811 of electromagnet 82 and releasing thearmature 112. The compression spring 111 then expands and the operatingrod 61 moves inward toward the left, lowering the yoke 4-5 into seatingcontact withthe legs 10 and 11 of core 9. In that connection, thecompression spring 111 is light, as noted, and exerts but enough forceto overcome the friction of the moving parts sufliciently to assure thatthe yoke 45 will move downward to effective position. Such downwardmovement of yoke 45 is accomplished by gravity supplemented by magneticattraction as yoke 45 approaches the core 9, as will be understood, andthe compression spring 111 at no time exerts sufiicient force to pullthe annature away from the electromagnet 82 when the latter isenergized. In its lowered effective position yoke 45 provides a path ofhigh magnetic permeability which shunts the magnetic fiux of core 9around the pole pieces 14 and 15 thereof. releases the rotor 8, if thecontrol valve 4- is then open, and valve 4 closes promptly, cutting offflow of gas to the main burner 69, which is then extinguished. Thearmature 112 then is in its inner position indicated in dotted lines inFigure l, with the electromagnet 82 and its housing 83 remaining in thenormal outer position thereof shown.

In the inward movement of rod 61 a finger 114 of an angle arm 115, fixedon rod 61 adjacent member 110,

contacts a pin 116 fixed to shaft 21 and extending substantiallyradially therefrom. The pin 116 is of such length andso disposed that inthe raised ineffective position of yoke 45 it clears finger 114, so asto permit freedom of turning of rotor 8 in either direction. When thecontrol valve 4 is in full open position, with rotor 8 in its dottedline position of Figure 2, the pin 116 extends toward member 110 and isdisposed in underlying substantially parallel relation to rod 61. If thepilot burner 70 is then extinguished, the rotor 8, and with it shaft 21,turns in clockwise direction, as viewed in Figures 2 and 5, and passesin front of finger 114 as yoke 45 approaches its full lowered oreffective position. At that time finger 114, in the continued inwardtravel of rod 61, contacts pin 116. Thereafter, the yoke 45 movesdownward a further and short distance, to its full lowered position. Inthis final downward movement of yoke 45, shaft 21 is turned a shortdistance clockwise, forcing control valve 4 tightly shut, after whichthat valve is maintained shut by the weight of yoke 45 and theattractive force then exerted between yoke 45 and core 9. That assuresthat valve 4 will be maintained sealed tightly closed when yoke 45 is inits lowered eflective position. If the control valve 4 is in closedposition when the pilot burner 70 is extinguished, the pin 116 will thenbe in a position but slightly in advance, counterclockwise, of itsposition That immediately shown in Figure 5. As the rod 61 approachesthe limit of its inward movement, finger 114 will contact pin 116 andvalve 4 will be urged toward its seat and held tightly closed, asbefore. As previously noted, the chamber or combustion space withinwhich the main burner 69 and the pilot burner 70 are located is ventedto atmosphere. Gas escaping from the pilot burner '70, afterextinguishment and before relighting thereof, will be in comparativelysmall volume and readily vented to atmosphere, incurring no risk ofexplosion when the pilot burner 76 is again lit. If desired, or ifconditions require, suitable means may be provided for cutting off flowof gas to the pilot burner, when the yoke is released and moved toeffective position, and reestablishing such flow during the resettingoperation and while the control valve 4 remains closed.

After release of the yoke 45 and closing of the control valve 4, if openwhen yoke 45 is released, it is necessary to perform a resettingoperation in order that the electromagnetic operator means may resumecontrol. In performing the resetting operation, the reset button isdepressed in opposition to compression spring 99, after the pilot burner70 has been relit and the thermocouple 72 has been heated sufficientlyto energize the coils 80 of electromagnet 82. When reset button 107 isdepressed plunger 103 forces arm 97 of hell crank 92 downward, swingingarm 94 thereof toward the left, as viewed in Figure 1. At that time, thearmature 112 is in its inner position indicated in dotted lines. As arm94 swings inward it moves the housing 83 and the parts carried therebyinward sufliciently to bring the poles of electromagnet 82 into closeproximity to armature 112, The armature 112 is then picked up by theelectromagnet 82 and held tightly seated on the pole ends thereof bymagnetic attraction. The reset button 107 is then released andcompression spring 99 returns bell crank lever 92 to its normalposition. In the return movement of lever 92, the housing 83 and theparts therein, including armature 112, are moved outward to normalposition. That pulls the operating rod 61 outward, to the right, andraises the yoke 45 to its upper ineffective position, through the bellcrank lever and associated parts, the mechanical advantage afforded bylever 55 being adequate for that purpose. The parts are then in theirpositions shown in Figure 1 and thereafter the control valve 4 may openand close under control of thermostat 28, as before, pilot burnerserving to ignite gas issuing from the main burner 69 whenever valve 4is opened, as will be understood.

It will be clear, from what has been said, that the control valve 4, ifopen, is immediately closed upon extinguishment of the pilot burner 70and flow of fuel to the main burner 4 is interrupted. Also, if controlvalve 4 is closed when pilot burner 70 is extingulished, it remainsclosed. In either case, flow of fuel to the main burner 4 is interruptedduring the resetting operation.

It will be understood that changes in detail may be resorted to withoutdeparting from the field and scope of our invention, and we intend toinclude all such variations, as fall within the scope of the appendedclaims, in this application in which the preferred form only of ourinvention has been disclosed.

We claim:

1. Control means comprising, means defining a low reluctance flux pathand an air gap operatively associated therewith, an actuatable member insaid air gap responsive to fiow of magnetic flux thereacross, means forproducing magnetic flux flow in said low reluctance path, conditionresponsive flux diverting means comprising a winding associated withsaid flux path and energized in response to a given condition bymagnetic flux afforded by said flux producing means for divertingmagnetic flux around a portion of said flux path for flow across saidair gap and actuation of said member, flux shunting means including amovable magnetic member having an inoperative position and having anoperative position bridging said air gap and affording a magnetic shunttherefor to prevent any substantial magnetic flux flow across said airgap and hence to prevent actuation of said actuatable memberirrespective of the response of said flux diverting means to saidcondition, and electromagnetic operating means for said magnetic member.

2. Control means comprising, means defining a low reluctance flux pathand an air gap operatively associated therewith, an actuatable member insaid air gap responsive to flow of magnetic flux thereacross, means forpro ducing magnetic flux flow in said low reluctance flux path means,condition responsive flux diverting means comprising a windingassociated with said flux path means and energizable in response to agiven condition by the magnetic flux afforded by said flux producingmeans for diverting magnetic flux around a portion of said flux path forflow across said air gap and actuation of said member, an electromagnetand armature movable to relative attracted and separated relation, and amagnetic member operatively related to said electromagnet and armatureand movable by relative movement of said electromagnet and armature fromattracted to separated relation from an inoperative position to anoperative position wherein it bridges said air gap and affords amagnetic shunt therefor to prevent any substantial magnetic flux flowacross said air gap and hence to prevent actuation of said actuatablemember irrespective of the response of said flux diverting means to saidcondition.

3. Control means comprising, means defining a low reluctance flux pathand an air gap operatively associated therewith, an actuatable member insaid air gap responsive to flow of magnetic flux thereacross, means forproducing'magnetic flux flow in said low reluctance flux path means,condition responsive flux diverting means comprising a windingassociated with said flux path means and energizable in response to agiven condition by the magnetic flux afforded by said flux producingmeans for diverting magnetic flux around a portion of said flux path forflow across said air gap and actuation of said member, resettable safetyshut-off means including an electromagnet and armature movable torelative attracted and separated relation and a magnetic memberoperatively related to said electro-magnet and armature and movable byrelative movement of said electromagnet and armature from attracted toseparated relation from an inoperative position to an operative positionwherein it bridges said air gap and affords a magnetic shunt therefor toprevent any substantial magnetic flux flow across said air gap and henceto prevent actuation of said actuatable member irrespective of theresponse of said flux diverting means to said condition, and reset meansfor simultaneously positioning said electromagnet and armature inattracted relation and said magnetic member in its said operativeposition to prevent actuation of said actuatable member during resettingof said electromagnet and armature.

4. Control means comprising, means defining a low reluctance flux pathand an air gap operatively associated therewith, an actuatable member insaid air gap responsive to flow of magnetic flux thereacross, means forpro ducing magnetic itluX flow in said low reluctance flux path means,condition responsive flux diverting means comprising a windingassociated with said flux path means and energizable in response to afirst condition by the magnetic flux afforded by said flux producingmeans for diverting magnetic flux around a portion of said flux for flowacross said air gap and actuation of said member, an electromagnet andarmature having a relative attracted position in which they are held inresponse to a second condition and movable to separated relation upontermination of said second condition, and a magnetic memher operativelyrelated to said electromagnct and arms ture and movable upon terminationof said 'second condition by relative movement of said electromagnet andarmature from attracted to separated relation from an inoperativeposition to an operative position wherein it bridges said air gap andaffords a magnetic shut therefor to prevent any substantial magneticflux flow across said air gap and hence to prevent actuation of saidactuatable member irrespective of the response of said flux divertingmeans to said first condition.

5. Electromagnetic control means comprising, a permeable core having afirst fiux path and a second flux path including an air gap, means forproducing a magnetic flux in said core, a member in said air gapactuatable in response to flow of magnetic flux 'thereacross, means forblocking flow of flux in a portion of said first flux path and tendingto force said blocked flux through said air gap, means affording a lowreluctance shunt path available to said blocked flux including apermeable member coacting with said core for bridging said air gap, andelectromagnetic means responsive to a given condition for holding saidpermeable member out of coacting engagement with said core, wherebyactuation of said member is effected by said flux blocking means butonly when said given condition is present.

6. Control means comprising, a magnetically permeable core provided withan air gap, an actuatable member in said air gap responsive to flow ofmagnetic flux thereacross, flux generating means energizable in responseto a given condition to produce magnetic flux flow in said core andacross said air gap for actuation of said actuatable member, fluxshunting means including a movable magnetic member having an inoperativeposition and having an operative position bridging said air gap andaffording a magnetic shunt therefor to prevent any substantial magneticflux flow across said air gap and hence to prevent actuation of saidactuatable member by flux generated by said flux generating means inresponse to said condition, and electromagnetic operating means for saidmagnetic member.

7. Control means comprising, a magnetically permeable core provided withan air gap, an actuatable member in said air gap responsive to flow ofmagnetic flux thereacross, flux generating means for producing magneticflux flow in said core and across said air gap for actuation of saidactuatable member, an electromagnet and armature movable to relativeattracted and separated relation, and a magnetic member operativelyrelated to said electromagnet and armature and movable by relativemovement of said electromagnet and armature from attracted to separatedrelation from an inoperative position to an operative position whereinit bridges said air gap and affords a magnetic shunt therefor to preventany substantial magnetic flux flow across said air gap and hence toprevent actuation of said actuatable member in response to generation offlux by said flux generating means.

8. Control means comprising, a magnetically permeable core provided withan air gap, an actuatable member in said air gap responsive to flow ofmagnetic flux thereacross, flux generating means for producing magneticflux flow in said core and across said air gap for actuation of saidactuatable member, resettable safety shut-oft means including a pair ofreleasable coupling means relatively movable to coupled and releasedrelation, and a magnetic member operatively related to one of saidmembers and movable by relative movement of said members from coupled toreleased relation from an inoperative posltion to an operative positionwherein it bridges said air gap and affords a magnetic shunt therefor toprevent any substantial magnetic flux flow across said air gap and henceto prevent actuation of said actuatable member in response to generationof flux by said flux generating means, and reset means forsimultaneously positioning said coupling members in coupled relation andsaid magnetic member in its said operative position to prevent actuationof said actuatable member during a resetting operation.

9. Control means comprising, a magnetically permeable core provided withan air gap, an actuatable member in said air gap responsive to flow ofmagnetic flux thereacross, flux generating means energizable in responseto a first condition for producing magnetic flux flow in said core andacross said air gap for actuation of said member, an electromagnet andarmature having a relative attracted position in which they are held inresponse to a second condition and movable to separated relation upontermi nation of said second condition, and a magnetic member operativelyrelated to said electromagnet and armature and movable upon terminationof said second condition by relative movement of said electromagnet andarmature from attracted to separated relation from an inoperativeposition to an operative position wherein it bridges said air gap andaffords a magnetic shunt there for to prevent any substantial magneticflux flow across said air gap and hence to prevent actuation of saidactu- 11 atable member by flux generated by said flux generating meansin response to said first condition.

10. Electromagnetic control means comprising, a permeable core providedWith an air gap, flux generating means for producing a magnetic flux insaid core and across said air gap, a member in said air gap actuatablein response to flow of magnetic flux thereacross, means afiording a lowreluctance shunt path for said flux including a permeable membercoacting with said core to bridge said air gap, and electromagneticmeans responsive to a given condition for holding said permeable memberout of coacting engagement with said core, whereby actuation of saidmember is effected by operation of said flux generating means but onlywhen said given condition is present.

References Qited in the file of this patent UNITED STATES PATENTS2,130,870 Boehne Sept. 20, 1938 2,179,305 Stickney Nov. 7, 19392,211,701 McGrath Aug. 13, 1940 2,306,578 Wetzel Dec. 29, 1942 2,385,530Paille Sept. 25, 1946 FORElGN PATENTS 373,376 Germany Apr. 11, 1923585,629 France Mar. 4, 1925 231,953 Switzerland July 14, 1944

